1. Field of the Invention
The present invention relates to a blade-type cleaning device for transfer-type electrophotographic copying machines, and more particularly to a blade-type cleaning device comprising a blade member of elastic material which is placed in pressing contact with the surface of a photoconductive member to remove residual toner from the surface.
2. Description of the Prior Art
Most of electrophotographic copying machines recently introduced employ blade-type cleaning devices for the reasons that they are compact in size and quite efficient in removing residual toner. However, there are at least two factors which must be considered in using the blade-type cleaning device one of which is the contact angle thereof relative to a photoconductive member in order to efficiently remove residual toner and the other of which is prevention of noise resulting from vibration of the blade-type cleaning device.
Blade-type cleaning devices heretofore known can be divided into two general groups, those in which, as shown in FIG. 1, of the two angles between the blade member 61 and line X.sub.1 tangent to the point of contact C.sub.1 between the blade member 61 and a photoconductive member 2 rotatable in the direction of the arrow a, the angle (hereinafter referred to as the "contact angle") .theta..sub.1 on the uncleaned portion of the photoconductive member 2 moving toward the blade is an obtuse angle, and those in which as shown in FIG. 2, the contact angle .theta..sub.2 between the blade member 61 and the tangent X.sub.2 to the contact point C.sub.2 is an acute angle.
In the arrangement shown in FIG. 1 in which the blade member 61 presses against the surface of the photoconductive member 2 at an obtuse contact angle .theta..sub.1, the frictional force between the photoconductive surface and the blade member 61 tends to compress the blade member and deforms the blade member 61 transversely of the axis thereof, so that the contact point C.sub.1 is subjected to a very great force. When rotation of the photoconductive member 2 is initiated, an especially high frictional force acts, and there is a possibility that the photoconductive member will be damaged.
The blade member 61 of FIG. 2 is not subjected to a friction force which tends to compress it, so that the possibility of this type of damage is not present. The arrangement of FIG. 2 nevertheless is deficient as compared with that of FIG. 1 in that the cleaning force is smaller and the blade member is likely to leave some residual toner on the photoconductive member depending on the angular setting of the blade member 61.
Another problem in employing the blade-type cleaning device is the occurrence of unpleasant noise caused by vibration of the blade member during the cleaning operation.
As has been discussed, the blade member of the cleaning device is held in contact with the surface of the photoconductive member at a pressure sufficient to remove toner particles from the surface. However, the rotation of photoconductive member will cause in succession the deformation of the blade member by the frictional force developed between the blade member and the photoconductive member as well as the repulsion due to the elasticity of the blade member as a result of said deformation. Because of this, vibration of high amplitude is generated to produce unpleasant noise. In order to prevent occurrence of such noise, there has been proposed in U.S. Pat. No. 4,152,067 a blade cleaning device which includes a vibration suppressing means mounted in a position with respect to the blade member for transmitting blade vibration to the suppressing means thereby damping the vibration. While this device may be quite effective to prevent occurrence of noise, the mechanism therefor is rather complicated and requires relatively voluminous support means for the blade member in order to accommodate said vibration suppressing means.